Cable operated controls are utilized in a number of control systems. For example, a clutch mechanism in a manual shift automobile is often connected by means of a flexible control cable to a clutch pedal mounted on the fire wall separating the engine compartment from the passenger compartment. In addition, flexible control cables are often utilized in brake systems where a brake is connected by means of a flexible control cable to a brake pedal also mounted on a fire wall.
The control cables in such systems often require adjustment in order to accommodate manufacturing tolerances in the cable itself or in the controlled member operated by the cable. Further adjustment may be required after a period of use to accommodate wear in the cable and attachments including sheaves or in the member controlled by the cable.
For example, in a manual shift system, the clutch mechanism facing plate wears during use resulting in the relatively heavy clutch spring drawing the control cable further towards the clutch mechanism and effectively shortening the cable whereby play will be introduced between the clutch pedal and the control cable. In brake systems, the opposite result occurs, that is, the effective length of the cable is lengthened as a result of the cables and attaching brackets taking a permanent deflection after a load is applied, again resulting in undesirable slack in the cables.
Such cable control systems can be adjusted manually to achieve the desired regulation but this usually requires shutting down of the system (in the case of an automobile, taking it to a garage) and obtaining the services of a mechanic.
Various structures have been proposed in the past to provide for a self-adjusting feature to assure proper tensioning of a control cable in a control system. Such devices have, however, been expensive to manufacture and often took up an undue amount of space in the engine compartment is limited and it is often difficult to provide space between the fire wall and a member to be controlled in which to position any self-adjusting control device.
In U.S. Pat. No. 4,378,713, there is disclosed and claimed a self-adjusting control cable device including a termination member which is adapted to be connected to the end of a cable extending to a controlled member such as a manual gear shift clutch mechanism or brake. The device also includes a connecting member adapted to connect with a flexible cable or rod leading to an actuation member such as a brake or clutch pedal. A main housing surrounds the termination and connecting members. A first spring is included for urging the termination member towards the connecting member and a second spring is included for urging the connecting member towards the termination member. A clutch means is carried by the connecting member and is adapted to engage and lock with the termination member when the connecting member is moved against the force of the second spring means by the actuation member. Engagement and locking of the clutch with the termination member will then pull the control cable to actuate the controlled member. When force is released from the actuation member, the second spring will move the connecting means and clutch means towards the termination member allowing the clutch means to disengage from the termination member. The termination member and control cable are then free to move with respect to the connecting means to accommodate for any wear in the system. Thus, in a brake system, the termination end will be urged to move towards the connecting member by the force of the first spring to take up any slack in the control cable. In the case of a clutch mechanism in a manual gear shift system, the termination end will be free to move away from the connecting member under the force of the heavy clutch spring of the clutch mechanism.
The main housing may be anchored to a wall, such as a fire wall separating the engine and operator compartments of a vehicle, or the device may be anchored between cable conduits extending between the controlled member and the fire wall.
In one form shown in U.S. Pat. No. 4,378,713, the clutch means comprises an annular collar which fits loosely around the termination member and which has an ear fitting into a slot in the connecting member. As the connecting member is moved away from the termination member, the annular collar will tilt such that its inside periphery will engage and lock with the termination member. Both the inside periphery of the annular collar and outside surface of the termination member may have serrated surfaces to better insure a locking engagement between the two parts.
In another form shown in U.S. Pat. No. 4,378,713, the connecting member comprises a circular housing and the clutch means comprises at least one radially movable collet piece carried by the connecting member. The connecting member has a tapered surface adapted to engage the collet piece and move it radially inwardly of the termination piece when the connecting member is moved away from the termination member by a force being applied to an actuation member. A third spring means is operatively positioned between the collet piece and the circular housing to urge the collet piece to a locked position with respect to the termination member. A stop is provided in the main housing to limit movement of the circular housing towards the termination member under the force of the second spring means and to also limit movement of the collet piece.
When the self-adjusting take up feature is utilized in connection with parking brake systems, the requirements become more stringent.
Federal Department of Transportation requires that all automobiles have a mechanical parking brake system capable of holding the vehicle on a 30% grade. Parking brake systems generally use a ratchet lock, hand or foot lever to apply a tension load to the rear brake shoes or pads. This load is usually transmitted by strand in a flexible conduit.
Proper adjustment at assembly line level has always been a problem for automotive manufacturers. Devices to impose a heavy load at time of initial adjustment are commonly used. The system will get out of adjustment if: the strand takes a permanent set from extension under load--the conduits shorten because of compression set--the swaged terminations slip on the strand--or the conduits seat in their respective anchorages.
Transporting the cars on carriers with the brake system under heavy loads and use by the owner after delivery may cause the system to get out of adjustment with high warranty cost to the manufacturer for manual adjustment by the dealer.
In U.S. application Ser. No. 832,526 filed Feb. 21, 1986 having a common assignee as the present application, a self-adjusting cable control device for automatically compensating for wear in a control cable system is disclosed and includes a termination member connected at one end of a control cable and a connecting member attached to an actuation member. The connecting member carries a clutch for locking with the termination member upon application of force to the actuation member. Spring means are provided to move the cable with respect to the actuation member when the clutch is disengaged from the termination member. The clutch comprises a plurality of collet members which are movable radially and longitudinally and surrounds the termination member. The collet members have conical surfaces at each end adapted to engage complementary conical surfaces on the connecting member and serrations which engage complementary serrations on the collet members. The control device further includes a release tube that is accessible from the exterior of the device and can be engaged and moved axially inwardly by a clip to disengage the collet members and thereby permit easy connection of the device to the cables. In addition, provision is made for a separate clip normally holding the tube in a position and operable to release the release tube and the collet members to operative position.
In accordance with the invention, the collet members are hinged to the termination member and are movable radially toward and away from the connecting member. Accordingly, less longitudinal movement is required between the termination member and connecting member permitting a more accurate adjustment.
It is an objective of the present invention to provide an improved control device to automatically impose a predetermined tension load at assembly line level. This loading is accomplished by the stored energy in the integral compression spring. Also of great importance is the continuing self-adjusting feature that compensates for stretch of strand-compressive set of conduits-slippage of terminations and seating of all of the system components. This provides for a long life properly adjusted parking brake system without any manual maintenance.
Among the further objectives of the invention are to provide a self-adjusting cable control device for automatic brake adjustment which is lower in cost, requires lower tooling cost, has improved ability for application to a wide range of vehicles that require special packaging considerations in the vehicle interior, is easily and safely installed in the vehicle assembly plant, and is easy to service in the field due to the ease of accessibility.
Further objectives are to provide such a self-adjusting cable control device which includes a quick release feature that facilitates installation, servicing and replacement, which can be safely locked for shipment to the vehicle assembly plant, which is shorter in length and width permitting installation in vehicles with little available space and reducing the overall mass subjected to vibration and resultant noise from contact with adjoining vehicle services.